Halogen-containing thermoplastic resin composition

ABSTRACT

A halogen-containing thermoplastic resin composition comprising a halogen-containing thermoplastic resin (A), a metallic soap (B) and an ash- and alkali metal-lean ethylene-vinyl acetate copolymer hydrolysate (C) having an ethylene content of 20 to 75 mole percent, a degree of saponification not less than 50 mole percent, an ash content not exceeding 300 ppm and an alkali metal content not exceeding 200 ppm, the proportions of (B) and (C) based on 100 parts of weight by (A) being 0.1 to 5 parts by weight and 0.1 to 5 parts by weight, respectively. The composition may further include, in addition to (A), (B) and (C) mentioned above, at least one compound (D) selected from the group consisting of β-diketone compounds, organic phosphorous esters and aminocarboxylic acid compounds, the proportion of (D) based on 100 parts by weight of (A) being 0.05 to 5 parts by weight, and/or at least one compound (E) selected from the group consisting of phenol derivatives and epoxy compounds, the proportion of (E) based on 100 parts by weight of (A) being 0.01 to 5 parts by weight.

BACKGROUND OF THE INVENTION

The present invention relates to a halogen-containing thermoplasticresin composition with improved stability against initial coloration,discoloration on aging and blackening.

The halogen-containing thermoplastic resin, represented by polyvinylchloride resin, give rise, on heating for melt-molding purposes, to apolyene structure with elimination of hydrochloric acid, undergoingyellowing. To enhance the thermal stability of the resin, it has beencommon practice to incorporate a metallic soap as a stabilizer in theresin. However, since the incorporation of a stabilizer metallic soapalone may lead to the so-called metal burning in a prolongedmelt-molding process, which causes blackening of the resin, it has beengenerally practiced to add an auxiliary stabilizer, such as polyols(e.g. pentaerythritol), organic phosphorous ester (e.g.triphenylphosphite), epoxy compounds (e.g. bisphenol A type epoxy resin)and so on.

Aside from the above-mentioned technology, Japanese Unexamined PatentApplication KOKAI 238345/1985 disclosed a material sharing with thepresent invention some of resin components, although the prior art isnot intended to enhance the thermal stability of halogen-containingthermoplastic resin.

Thus, the above-mentioned patent literature describes a resincomposition consisting of (a) a thermoplastic resin (inclusive ofpolyvinyl chloride resin), (b) an ethylene-vinyl acetate copolymerhydrolysate, and (c) a salt or oxide containing at least one elementselected from Groups I, II and III of Periodic Table of the Elements andmentions that this composition assures a marked improvement incompatibility.

In addition, Japanese Unexamined Patent Application KOKAI 69955/1977discloses a polyvinyl chloride barrier packaging composition consistingessentially of a mixture of polyvinyl chloride and 10 to 30 weightpercent, based on polyvinyl chloride, of an ethylenevinyl alcoholcopolymer which shares some resin components with the composition of thepresent invention.

However, the use of a metallic soap as a stabilizer in combination withan auxiliary stabilizer has the disadvantage that where the auxiliarystabilizer is a polyol, the resulting composition is inadequate incompatibility and dispersibility so that the plate-out phenomenon(sticking of the batch to the roll) in the roll mixing stage inevitable,that where the auxiliary stabilizer is an organic phosphorous ester, itis hydrolyzed on absorption of moisture to lose its expected effect inpart, and that where an epoxy compound is used as the auxiliarystabilizer, yellowing and plate-out cannot be sufficiently inhibited.

The composition described in Japanese Unexamined Patent ApplicationKOKAI 69955/1985 is claimed to offer improved compatibility but has roomfor improvement in thermal stability.

The composition described in Japanese Unexamined Patent ApplicationKOKAI 69955/1977 is conductive to reduce oxygen permeability withsuppression of water vapor permeation but is poor in melt-moldabilityand in prevention of discoloration, thus being of no great use inpractical applications. Furthermore, since this composition is rich inethylene-vinyl alcohol copolymer, the inherent characteristics ofpolyvinyl chloride resin are not available, thus delimiting its range ofapplication.

The present invention has been accomplished to provide ahalogen-containing thermoplastic resin composition having markedlyimproved thermal stability.

Summary of the Invention

The present invention relates to a halogen-containing thermoplasticresin composition comprising a halogen-containing thermoplastic resin(A), a metallic soap (B) and an ash- and alkali metal-leanethylene-vinyl acetate copolymer hydrolysate (C) having an ethylenecontent in the range of 20 to 75 mole percent, a degree ofsaponification not less than 50 mole percent, an ash content not morethan 300 ppm and an alkali metal content not more than 200 ppm, theproportions of (B) and (C) based on 100 parts by weight of (A) being 0.1to 5 parts by weight and 0.1 to 5 parts by weight, respectively.

In a preferred embodiment, the present invention relates to ahalogen-containing thermoplastic resin composition which comprises, inaddition to said halogen-containing thermoplastic resin (A), metallicsoap (B) and ash- and alkali metal-lean ethylene-vinyl acetate copolymerhydrolysate (C) mentioned above, at least one compound (D) selected fromthe group consisting of β-diketone compounds, organic phosphorous estersand aminocarboxylic acid compounds, the proportion of (D) based on 100parts by weight of (A) being 0.05 to 5 parts by weight.

In still another preferred embodiment, the halogen-containingthermoplastic resin composition of the invention further comprises, inaddition to (A), (B), (C) and (D) mentioned above, at least one compound(E) selected from the group consisting of phenol derivatives and epoxycompounds, the proportion of (E) based on 100 parts by weight of (A)being 0.01 to 5 parts by weight.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is described in detail below.

Halogen-containing thermoplastic resin (A)

As examples of halogen-containing thermoplastic resin (A), there may bementioned polyvinyl chloride resin, polyvinylidene chloride resin,chlorinated polyethylene, chlorinated polypropylene, chlorinatedpolyethylene-vinyl acetate copolymer and chlorosulfonated polyethylene.Particularly useful are polyvinyl chloride type resins, i.e. vinylchloride homopolymer and copolymers of vinyl chloride with othercomonomers.

Metallic soap (B)

As examples of metallic soap (B), there may be mentioned Group II metalsalts of higher fatty acids, resin acid, naphthenic acid and so on. AsGroup II metals, there may be mentioned magnesium, calcium, strontium,barium, zinc, cadmium and so on. Particularly useful are the salts ofhigher fatty acids, such as stearic acid, lauric acid, ricinolic acid,etc., with zinc, magnesium, calcium, barium or cadmium. Particularly,the zinc salts are especially effective and, therefore, it is preferableto use a higher fatty acid zinc salt at least in part. Moreover, whilethe metallic soaps mentioned above can be used singly, a greaterstabilizing effect can be achieved by using two or more of them incombination.

Ethylene-vinyl acetate copolymer hydrolysate (C)

As the aforesaid ethylene-vinyl acetate copolymer hydrolysate (C), acopolymer having an ethylene content of 20 to 75 mole percent and adegree of saponification of its vinyl acetate unit not less than 50 molepercent is used.

Any ethylene-vinyl acetate copolymer whose composition is outside of theabove range is insufficient to provide the desired degree of improvementin the thermal stability of halogen-containing thermoplastic resin (A).It should be understood that provided the copolymer composition is notdeviant from the aforesaid range, (A) may include other comonomer unitsin a small proportion.

The ethylene-vinyl acetate copolymer hydrolysate (C) can generally beprepared by hydrolyzing (saponifying) an ethylene-vinyl acetatecopolymer with the aid of an alkali catalyst. However, the industrialwater and reagents used generally contain metal salts as impurities andthe saponification catalyst (an alkali metal hydroxide) remains as thealkali metal acetate after the reaction, with the result that suchimpurities and alkali metal acetate tend to be contained in thesaponified polymer separated by precipitation or filtration from thesaponification reaction mixture. Though it depends on various factorssuch as the ethylene content of the resin, degree of saponification,conditions of saponification reaction, etc., the ash and alkali metalcontents of the ethylene-vinyl acetate copolymer hydrolysate so obtainedare usually about 5,000 to 50,000 ppm and about 4,000 to 40,000 ppm,respectively.

The terms `ash content` are used herein to mean the value found asfollows. The ethylene-vinyl acetate copolymer hydrolysate is dried,taken in a platinum evaporating dish and carbonized by means of anelectric heater and a gas burner. The carbonized resin is then chargedinto an electric furnace at 400° C. The furnace temperature is thenincreased to 700° C., at which temperature it is thoroughly reduced toashes over 3 hours. The ashes are taken out from the furnace, allowed tocool over 5 minutes and further allowed to stand in a desiccator for 25minutes. Finally, the ashes were accurately weighed.

The terms `alkali metal content` are used herein to mean the value foundas follows. After the ethylenevinyl acetate copolymer hydrolysate isreduced to ashes as in the determination of ash content, the ashes aredissolved in an aqueous solution of hydrogen chloride under warming andthe solution is subjected to atomic absorption spectrometry.

The ethylene-vinyl acetate copolymer hydrolysate (C) to be used inaccordance with the invention preferably has an ash content, asdetermined by the above procedure, not more than 300 ppm, more desirablynot more than 50 ppm, and for still better results not more than 20 ppmand an alkali metal content, also as determined by the above-describedprocedure, not more than 200 ppm, more desirably not more than 35 ppm,and for still better results not more than 5 ppm. The lower is the ashcontent or/and the alkali metal content, the more pronounced is theeffect on thermal stability, particularly in terms of prevention ofinitial coloration. The ash and alkali metal contents are preferably aslow as possible within the respective ranges mentioned above but becauseof various limitations imposed on purification in commercial production,the practical lower limits are about 1 ppm for ashes and about 0.5 ppmfor alkali metal.

The aforementioned ash- and alkali metal-lean ethylene-vinyl acetatecopolymer hydrolysate (C) can be prepared as follows. The powders,granules or pellets of ethylene-vinyl acetate copolymer hydrolysateobtained by said saponification reaction are washed thoroughly with anaqueous solution of acid, preferably a weak acid, to remove the saltresponsible for said ashes and alkali metal and are then preferablyrinsed (with deionized water; the same applies hereinafter) to removethe absorbed acid from the resin and dried.

As examples of the weak acid mentioned above, there may be employedacetic acid, propionic acid, glycolic acid, lactic acid, adipic acid,azelaic acid, glutaric acid, succinic acid, benzoic acid, isophthalicacid, terephthalic acid and so on. Generally, a weak acid with a pKavalue not less than 3.5 at 25° C. is preferred.

After the above weak acid treatment and either before or after rinse,there is preferably carried out a further treatment with a diluteaqueous solution of strong acid, for example an organic acid with a pKavalue not exceeding 2.5 at 25° C., such as oxalic acid, maleic acid,etc., or mineral acids such as phosphoric acid, sulfuric acid, nitricacid, hydrochloric acid and so on. By this strong acid treatment,removal of the alkali metal can be made more effectively.

Compound (D)

As compound (D), at least one compound selected from the groupconsisting of β-diketone compounds, organic phosphorous esters andaminocarboxylic acid compounds is employed.

The aforesaid β-diketone compounds include, among others,dibenzoylmethane, benzoylacetone, tribenzoylmethane,diacetylacetobenzene, stearoylacetophenone, palmitoylacetophenone,lauroylacetophenone, p-methoxy stearoylacetophenone,stearoylbenzoylmethane, acetoacetic esters, acetylacetone,1,1-diacetylacetone, triacetylmethane, stearoylacetone,palmitoylacetone, lauroylacetone, stearoyloctanone, heptane-2,4-dione,decane-2,4-dione, ethyl nonane-2,4-dionecarboxylate,8-methylnona-7-ene-2,4-dione, 1-benzoyloctan-2-one,2-methyldecan-2-ene-6,8-dione,methylene-2,2'-bis-(cyclohexane-1,3-dione),1,4-diphenylbutane-1,3-dione, 1-phenyl-2-allyl-1,3-butanedione,benzoylacetaldehyde, 2-methyl-2-acetylacetaldehyde, dehydroacetic acid,dehydroacetates and so on.

The aforesaid organic phosphorous esters include, among others, triarylphosphites such as triphenyl phosphite, tris(p-nonylphenyl)phosphite,etc.; alkyl aryl phosphites, for example monoalkyl diphenyl phosphitessuch as diphenyl isooctyl phosphite, diphenyl isodecyl phosphite, etc.and dialkyl monophenyl phosphites such as phenyl diisooctyl phosphite,phenyl diisodecyl phosphite, etc.; and trialkyl phosphites such astriisooctyl phosphite, tristearyl phosphite and so on.

The aforesaid aminocarboxylic acid compounds include, among others,aminocarboxylic compounds such as glycine, alanine, lysine, triptophan,acetylglutamic acid, acetylphenylalanine, acetylmethionine,pyrrolidonecarboxylic acid, β-aminocrotonic acid, α-aminoacrylic acid,α-aminoadipic acid, etc. and the corresponding esters. The alcoholcomponents of such esters include, among others, monohydric alcoholssuch as methanol, ethanol, propanol, isopropyl alcohol, butanolα-ethylhexanol, octanol, isooctyl alcohol, lauryl alcohol, stearylalcohol, etc. and polyhydric alcohols such as ethylene glycol, propyleneglycol, 1,3-butanediol, 1,4-butanediol, glycerol, diglycerol,trimethylolpropane, pentaerythritol, dipentaerythritol, sorbitol,mannitol and so on.

Compound (E)

As compound (E), use is made of at least one compound selected from thegroup consisting of phenol derivatives and epoxy compounds.

The aforesaid phenol derivatives include, among others,2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol,4,4'-thiobis(6-t-butylphenol),2,2,'-methylene-bis(4-metyl-6-t-butylphenol),tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane,octadecyl 3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate,4,4'-thiobis(6-t-butylphenol),N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxyhydrocinnamide) and so on.

The aforesaid epoxy compounds include, among others, various animal orvegetable oils such as epoxidized soybean oil, epoxidized linseed oil,epoxidized fish oil, epoxidized beef tallow oil, etc., epoxidized fattyacid esters such as epoxidized methyl stearate, epoxidized butylstearate, etc., epoxidized alicyclic compounds such as epoxidized butyltetrahydrophthalate, epoxidized octyl tetrahydrophthalate, etc.;glycidyl ethers or esters such as bisphenol A diglycidyl ether, glycidylmethacrylate and its polymer, etc., and epoxy-containing high polymerssuch as epoxidized polybutadiene, epoxidized acrylonitrilebutadienerubber and so on.

Formation

The proportions of the above-mentioned various components based on 100parts by weight of said halogen-containing thermoplastic resin (A) areas follows.

Metallic soap (B)

0.1 to 5 and preferably 0.5 to 4 parts by weight

Ethylene-vinyl acetate copolymer hydrolysate (C)

0.1 to 5 and preferably 0.2 to 4 parts by weight

Compound (D)

0 to 5, preferably 0.05 to 5, and for still better results, 0.1 to 3parts by weight

Compound (E)

0 to 5, preferably 0.01 to 5, and for still better results, 0.01 to 4parts by weight

In the above formulation, the weight ratio of ethylene-vinyl acetatecopolymer hydrolysate (C) to metalic soap (B) [(C)/(B)] is preferablywithin the range of 0.05 to 2 and, for better results, within the rangeof 0.1 to 1.

If either (B) or (C) is absent or the ratio deviates from the aboverange, the desired degree of improvement in thermal stability willhardly be obtained.

While the effect of the invention can be well implemented by addition of(B) and (C) to (A), the further addition of (D) or (D) plus (E)contributes to a further improvement in thermal stability.

Other additives

In the halogen-containing thermoplastic resin composition of theinvention, there may be further incorporated, as necessary, variousadditives known for incorporation in halogen-containing thermoplasticresin compositions, such as plasticizers, dyes and pigments, fillers,lubricating agents, antistatic agents, surfactants, chelating agents,reinforcing materials, foaming agents, impact resistance improvingagents (ethylene- vinyl acetate copolymer, acrylic copolymer, ABS resin,MBS resin, etc.) and so on. It is also possible to incorporateantioxidants, ultraviolet absorbers and other auxiliary stabilizers(e.g. polyols, hydrotalcite compounds of the general formula M_(x)Al_(y) (OH)_(2x+3y-2z) (E)_(z).aH₂ O wherein M=Mg, Ca or Zn; E=CO₃ orHPO₃ ; x, y and z each is a positive integer; a is equal to zero ormeans a positive integer). Furthermore, within limits not contrary tothe objects of the invention, other thermoplastic resins may also beincorporated in the halogen-containing thermoplastic resin compositionof the invention.

A plasticizer such as phthalic acid esters, aliphatic dibasic acidesters, trimellitic acid esters, phosphate esters, fatty acid esters,epoxy plasticizers, polyester type plasticizers, paraffin chloride, maybe added in appropriate proportions relative to halogen-containingthermoplastic resin (A). In the stabilizing effect of said variousadditives according to the invention on resin (A), such a plasticizerplays a significant part, and this stabilizing effect is pronounced whenthe plasticizer is added in a proportion up to about 40 parts by weightbased on 100 parts by weight of (A).

Melt-molding

As melt-molding technologies compatible with the halogen-containingthermoplastic resin composition of the invention, calendering, extrusionmolding, injection molding, blow molding and other processes may bementioned by way of example.

Thus, in accordance with the present invention, the thermal stability(stability against initial coloration, discoloration on aging andblackening) of halogen-containing thermoplastic resin (A) can bemarkedly improved by addition of said metallic soap (B) andethylene-vinyl acetate copolymer hydrolysate (C), preferably togetherwith said compound (D) or (E) or said compounds (D) and (E) at thedefined levels. As to the roles played by these additives, the metallicsoap (B) is supposed to act as a stabilizer and the ethylene-vinylacetate copolymer hydrolysate (C), compound (D) and compound (E) asauxiliary stabilizers.

The composition of the invention shows no plate-out phenomena duringcalendering and permits extrusion molding in a long run. Moreover, theresulting moldings are free of discoloration.

Therefore, the present invention is a remarkable contribution to theindustry engaged in the molding of polyvinyl chloride and otherhalogen-containing thermoplastic resins.

EXAMPLES

The following examples are further illustrative of the composition ofthe invention. In the examples, all `parts` and `%` are by weight unlessotherwise indicated and the water used is invariably deionized water.

Ethylene-vinyl acetate copolymer hydrolysate (C)

An ash- and alkali-lean ethylene-vinyl acetate copolymer hydrolysate (C)was prepared as follows.

(C-0)

An ethylene-vinyl acetate copolymer with an ethylene content of 44 mole% was dissolved in methanol to give a 40% solution and 1,000 parts ofthe solution was fed to a pressure-resistant reactor, in which it washeated at 110° C. with stirring. Then, 40 parts of a 6% solution ofsodium hydroxide in methanol and 2,500 parts of methanol werecontinuously fed to the reactor and the hydrolysis reaction wasconducted for 2.5 hours, with the byproduct methyl acetate and excessmethanol being constantly distilled out from the reaction system. Theprocedure gave an ethylene-vinyl acetate copolymer hydrolysate with adegree of saponification of the vinyl acetate unit being 99.5 mole %.

After completion of the hydrolysis reaction, 450 parts of 30% aqueousmethanol was introduced and the excess methanol was distilled off togive a 39% solution in water-methanol (3:7).

This solution, held at 50° C., was extruded, in the form of strands,through a nozzle (orifice diameter 4 mm) into a water-methanol (9:1)coagulation bath (100 mm wide, 4,000 mm long, 100 mm deep; maintained at5° C.) at a rate of 1.5 l/hr. After coagulation, the strands were takenup on a roll disposed at one side of the coagulation bath at a linearspeed of 2 m/min. and cut with a cutter to give white, porous pellets 4mm in diameter and 4 mm in length.

The above pellets of ethylene-vinyl acetate copolymer hydrolysate had anash content of 7,400 ppm and a sodium metal content of 4,800 ppm.

This ethylene-vinyl acetate copolymer hydrolysate is designated as(C-0).

(C-1)

In 300 parts of 0.3% aqueous acetic acid were immersed 100 parts of theabove pellets (C-0) for washing with stirring for 1 hour at 30° C. Thisprocedure (weak acid treatment) was repeated twice. The slurry was thenfiltered and 300 parts of water were added to the pellets again. Theresulting slurry was stirred at 30° C. for 1 hour. This rinse wasrepeated 3 times and the rinsed pellets were dried.

The above rinsed pellets of ethylene-vinyl acetate copolymer hydrolysatehad an ash content of 6 ppm and a sodium metal content of 2.7 ppm.

This ethylene-vinyl acetate copolymer hydrolysate was designated as(C-1).

(C-2)

Prior to the above rinse procedure, the (C-1) pellets washed with weakacid as above were subjected to a strong acid treatment using 230 partsof a 0.003% aqueous solution of phosphoric acid under stirring at 30° C.for 1 hour and, then, subjected to 3 cycles of rinse as in the case ofproduction of (C-1), followed by drying.

The resulting pellets of ethylene-vinyl acetate copolymer hydrolysatehad an ash content of 10 ppm and a sodium metal content of 1.4 ppm.

This ethylene-vinyl acetate copolymer hydrolysate was designated as(C-2).

(C-3)

The pellets (C-0) were washed in the same manner as in the preparationof (C-1) but the number of washing cycles was reduced to give thefollowing pellets.

(C-3a)

An ethylene-vinyl acetate copolymer hydrolysate with an ash content of41 ppm and a sodium metal content of 26 ppm.

(C-3b)

An ethylene-vinyl acetate copolymer hydrolysate with an ash content of152 ppm and a sodium metal content of 96 ppm.

(C-3c)

An ethylene-vinyl acetate copolymer hydrolysate with an ash content of252 ppm and a sodium metal content of 153 ppm.

(C-3d)

An ethylene-vinyl acetate copolymer hydrolysate with an ash content of415 ppm and a sodium metal content of 305 ppm.

(C-4)

The pellets (C-0) mentioned above were washed in the same manner as inthe preparation of (C-1) except that the acetic acid concentration ofthe weak acid bath was reduced to give pellets of an ethylene-vinylacetate copolymer hydrolysate having an ash content of 240 ppm and asodium metal content of 170 ppm. This ethylene-vinyl acetate copolymerhydrolysate was designated as (C-4).

(C-5)

To a mixed solution of 1,950 parts of methanol, 925 parts of water, 182parts of sodium hydroxide and 38 parts of acetone was added 1,124 partsof a suspension-polymerized ethylene-vinyl acetate copolymer (ethylenecontent 71 mole %, water content 11.0%) and the hydrolysis reaction wasconducted at 30° C. for 3 hours and, then, at 35° C. for a further 3hours, with constant stirring. The resulting slurry was centrifuged.

Then, 100 parts of the copolymer hydrolysate thus separated was mixedwith 300 parts of a 1% aqueous solution of acetic acid and stirred at30° C. for 1 hour. This washing procedure was repeated twice.

The slurry was then filtered and the resulting polymer was immersed in300 parts of a 0.5% aqueous solution of phosphoric acid and stirred at30° C. for 1 hour. This strong acid washing procedure was carried outonce.

The slurry was then filtered and the resulting resin was mixed with 300parts of water and stirred at 30° C. for 1 hour. This rinse procedurewas repeated 3 times, after which the resin was dried in vacuo at roomtemperature.

The resulting ethylene-vinyl acetate copolymer hydrolysate had asaponification degree of 61.2 mole %, an ash content of 15 ppm and asodium metal content of 4.0 ppm.

This ethylene-vinyl acetate copolymer hydrolysate was designated as(C-5).

(C-6)

After the hydrolysis reaction conducted as in the preparation of (C-5),the resulting slurry was centrifuged and the primary saponificationproduct thus obtained was added to a mixed solution of 2,000 parts ofmethanol, 500 parts of water, 200 parts of sodium hydroxide and 38 partsof acetone and stirred at 30° C. for 2 hours, then at 35° C. for 2hours, and finally at 40° C. for 2 hours for secondary saponification.The slurry was then centrifuged.

As in the case of (C-5), the resin was subjected to weak acid treatment,strong acid treatment and rinse procedure and dried in vacuo at roomtemperature.

The resulting ethylene-vinyl acetate copolymer hydrolysate had asaponification degree of 91.0 mole %, an ash content of 45 ppm and asodium metal content of 21 ppm.

The above ethylene-vinyl acetate copolymer hydrolysate was designated as(C-6).

The assays of ashes and sodium metal were carried out as follows.

(Ashes)

About 80 g of each dried sample was accurately weighed and a portion(about 10 g) was put in a calibrated platinum evaporating dish andcarbonized with an electric heater. This procedure was repeated withincrements of about 10 g of the sample. Finally, the carbonized samplewas incinerated in the flame of a gas burner until smokes ceased toemerge.

The above platinum evaporating dish was placed in an electric furnace atabout 400° C. and, with the dish mostly covered up with a porcelaincrucible cover, the furnace temperature was gradually increased to 700°C. This temperature was maintained for 3 hours for complete reduction toash and the sample was then taken out from the furnace and allowed tocool for 5 minutes. It was further allowed to stand in a desiccator for25 minutes and the ashes were accurately weighed.

Sodium metal

About 10 g of each dried sample was accurately weighed into a platinumcrucible and reduced to ash in the same manner as above. The platinumcrucible was charged with 2 ml of special reagent grade hydrochloricacid and 3 ml of pure water and the sample was dissolved by heating withan electric heater. Using purified water, the solution was flushed intoa 50 ml measuring flask and deionized water was further added up to themarked line for preparation of a sample for atomic absorptionspectrometry.

Using a separately prepared standard solution (sodium metal 1 ppm, HClapprox. 0.5 N) as blank, atomic absorption spectrometry was carried outand the amount of sodium metal was estimated from the absorbance ratio.The instrument parameters were as follows.

Instrument : Hitachi Model 180-30 atomic absorption/flamespectrophotometer

Wavelength : 589.0 nm

Flame : acetylene-air

Compound (D)

As examples of compound (D), the following compounds were provided.

(D-1) : dehydroacetic acid

(D-2) : stearoylbenzoylmethane

(D-3) : dibenzoylmethane

(D-4) : diphenyl isodecyl phosphite

(D-5) : diphenyl isooctyl phosphite

(D-6) : triphenyl phosphite

(D-7) : 1,4-butanediol bis-β-aminocrotonate

(D-8) : stearyl β-aminocrotonate

(D-9) : acetylglutamic acid

Compound (E)

As examples of compound (E), the following compounds were provided.

(E-1) :tetrakis[methylene-3-(3',5'-di-t-butyl4'-hydroxyphenyl)propionate]methane(Irganox 1010, Ciba-Geigy)

(E-2) : N,N'-hexamethylene-bis(3,5-di-t-butyl 4-hydroxyhydrocinnamide)(Irganox 1098, Ciba-Geigy)

(E-3) : octadecyl 3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate(Irganox 1076, Ciba-Geigy)

(E-4) : bisphenol A diglycidyl ether

(E-5) : epoxidized soybean oil

(E-6) : epoxidized linseed oil

EXAMPLES 1 TO 10; COMPARATIVE EXAMPLES 1 TO 9

    ______________________________________                                        Polyvinyl chloride with a degree of                                                                      100    Parts                                       polymerization = 800 (A)                                                      Dioctyl phthalate (plasticizer)                                                                          20     Parts                                       Calcium stearate (B)       1      Part                                        Zinc stearate (B)          1      Part                                        Ethylene-vinyl acetate copolymer hydrolysate (C),                                                       As mentioned                                        to be described hereinafter                                                                             hereinafter                                         Compound (D), to be described hereinafter                                                               As mentioned                                                                  hereinafter                                         Compound (E), to be described hereinafter                                                               As mentioned                                                                  hereinafter                                         ______________________________________                                    

The above composition was subjected to preliminary mixing and, then,kneading by means of a 6"(dia.)×12" roll at 170° C. for 5 minutes togive a 0.5 mm thick sheet.

From this sheet, a 50×60 mm testpiece was cut out and allowed to standin a gear oven at 180° C. for testing its thermal stability.

The results are shown in Table 1. The evaluation of thermal stabilitywas made according to the following 9-point schedule.

1 : colorless

2 : pale pink or pale yellow

3 : pale orange

4 : light pink

5 : light orange

6 : yellow-orange

7 : orange

8 : black spots

9 : black

EXAMPLE 1

(C) component : (C-1), 0.5 Part

(D) component : (D-1), 0.3 Part

EXAMPLE 2

(C) component : (C-1), 0.5 Part

(D) component : (D-4), 0.3 Part

EXAMPLE 3

(C) component : (C-1), 0.5 Part

(D) component : (D-7), 0.3 Part

EXAMPLE 4

(C) component : (C-1), 0.5 Part

(D) component : (D-1), 0.3 Part

(E) component : (E-1), 0.1 Part

EXAMPLE 5

(C) component : (C-1), 0.5 Part

(D) component : (D-4), 0.3 Part

(E) component : (E-2), 0.1 Part

EXAMPLE 6

(C) component : (C-1), 0.5 Part

(D) component : (D-7), 0.3 Part

(E) component : (E-3), 0.1 Part

EXAMPLE 7

(C) component : (C-1), 0.5 Part

(D) component : Not added

(E) component : Not added

EXAMPLE 8

(C) component : (C-1), 0.5 Part

(D) component : Not added

(E) component : (E-1), 0.1 Part

EXAMPLE 9

(C) component : (C-1), 0.5 Part

(D) component : Not added

(E) component : (E-2), 0.1 Part

EXAMPLE 10

(C) component : (C-1), 0.5 Part

(D) component : Not added

(E) component : (E-3), 0.1 Part

COMPARATIVE EXAMPLE 1

(C) component : Not added

(D) component : Not added

(E) component : Not added

COMPARATIVE EXAMPLE 2

(C) component : (C-0), 0.5 Part

(D) component : Not added

(E) component : Not added

COMPARATIVE EXAMPLE 3

(C) component : Not added

(D) component : (D-1), 0.3 Part

(E) component : Not added

COMPARATIVE EXAMPLE 4

(C) component : Not added

(D) component : (D-4), 0.3 Part

(E) component : Not added

COMPARATIVE EXAMPLE 5

(C) component : Not added

(D) component : (D-7), 0.3 Part

(E) component : Not added

COMPARATIVE EXAMPLE 6

(C) component : Not added

(D) component : (D-1), 0.3 Part

(E) component : (E-1), 0.1 Part

COMPARATIVE EXAMPLE 7

(C) component : Not added

(D) component : (D-4), 0.3 Part

(E) component : (E-2), 0.1 Part

COMPARATIVE EXAMPLE 8

(C) component : Not added

(D) component : (D-7), 0.3 Part

(E) component : (E-3), 0.1 Part

EXAMPLES 11 TO 16

Using the following formulas, sheets were manufactured and tested forthermal stability in otherwise the same manner as Examples 1 to 10.

    ______________________________________                                        Polyvinyl chloride with a degree of                                                                      100    Parts                                       polymerization = 800 (A)                                                      Dioctyl phthalate (plasticizer)                                                                          20     Parts                                       Barium stearate (B)        1      Part                                        Zinc laurate (B)           1      Part                                        Ethylene-vinyl acetate copolymer hydrolysate (C),                                                       As mentioned                                        to be described hereinafter                                                                             hereinafter                                         Compound (D), to be described hereinafter                                                               As mentioned                                                                  hereinafter                                         Compound (E), to be described hereinafter                                                               As mentioned                                                                  hereinafter                                         ______________________________________                                    

The results are also shown in Table 1. The evaluation of thermalstability was made in the same manner as above, using the same 9-pointrating schedule.

EXAMPLE 11

(C) component : (C-2), 1.0 Part

(D) component : (D-2), 0.4 Part

(E) component : (E-1), 0.2 Part

EXAMPLE 12

(C) component : (C-3a), 1.0 Part

(D) component : (D-5), 0.4 Part

(E) component : (E-1), 0.2 Part

EXAMPLE 13

(C) component : (C-4), 1.0 Part

(D) component : (D-8), 0.4 Part

(E) component : (E-1), 0.2 Part

EXAMPLE 14

(C) component : (C-2), 1.5 Part

(D) component : (D-3), 0.5 Part

(E) component : (E-4), 0.5 Part

EXAMPLE 15

(C) component : (C-3a), 1.5 Part

(D) component : (D-6), 0.5 Part

(E) component : (E-5), 3.0 Part

EXAMPLE 16

(C) component : (C-5), 2.5 Part

(D) component : (D-9), 0.5 Part

(E) component : (E-6), 3.0 Part

EXAMPLE 17

    ______________________________________                                        Vinylidene chloride-methyl acrylate copolymer                                                            100    Parts                                       (methyl acrylate content 7 mole %)                                            Dioctyl phthalate (plasticizer)                                                                          20     Parts                                       Calcium stearate (B)       1      Part                                        Zinc stearate (B)          2      Parts                                       Ethylene-vinyl acetate copolymer hydrolysate (C-1)                                                       1      Part                                        (D-7)                      0.3    Part                                        (E-1)                      0.1    Part                                        ______________________________________                                    

The above composition was extruded into a 0.5 mm thick sheet and atestpiece thereof allowed to stand in a gear oven at 170° C. for testingits thermal stability.

The extrusion-molding conditions were as follows.

Extruder : 40 mm (dia.)

Screw : L/D 23, compression ratio 3.2

Cylinder temperature (MAX) : 170° C.

Head temperature : 170° C.

Die temperature : 170° C.

The results are shown in Table 1.

EXAMPLES 18 AND 19; COMPARATIVE EXAMPLE 9

The procedure of Example 17 was repeated except that the formulation wasvaried as follows. The results are also shown in Table 1.

EXAMPLE 18

(C) component : (C-1), 1.0 Part

(D) component : Not added

(E) component : (E-1), 0.1 Part

EXAMPLE 19

(C) component : (C-1), 1.0 Part

(D) component : (D-7), 0.3 Part

(E) component : Not added

COMPARATIVE EXAMPLE 9

(C) component : Not added

(D) component : (D-7), 0.3 Part

(E) component : (E-1), 0.1 Part

EXAMPLE 20

    ______________________________________                                        Chlorinated polyethylene (Cl content 40%)                                                                100    Parts                                       Dioctyl phthalate (plasticizer)                                                                          20     Parts                                       Triazine type vulcanizer   1      Part                                        Mercaptobenzothiazole type accelerator                                                                   2      Parts                                       Calcium stearate (B)       1      Part                                        Zinc stearate (B)          2      Parts                                       Ethylene-vinyl acetate copolymer hydrolysate (C-2)                                                       1      Part                                        (D-1)                      0.3    Part                                        (E-5)                      3      Parts                                       ______________________________________                                    

The above composition was molded (kneading by roll at 140° C. for 5min.; vulcanizing at 160° C. for 20 min.) to give a 1 mm thick sheet.

The sheet was allowed to stand in a gear oven at 170° C. for a thermalstability test.

The results are shown in Table 1.

EXAMPLES 21 AND 22; COMPARATIVE EXAMPLE 10

Using the following formulations, sheets were manufactured in otherwisethesame manner as Example

EXAMPLE 21

(C) component : (C-2), 1.0 Part

(D) component : Not added

(E) component : (E-5), 3.0 Parts

EXAMPLE 22

(C) component : (C-2), 1.0 Part

(D) component : (D-1), 0.3 Part

(E) component : Not added

COMPARATIVE EXAMPLE 10

(C) component : Not added

(D) component : (D-1), 0.3 Part

(E) component : (E-5), 3.0 Parts

                  TABLE 1                                                         ______________________________________                                        (Result of evaluation of thermal stability)                                   Time (minutes)                                                                0          10     20     30  40  50  60  80  100  120                         ______________________________________                                        Example 1                                                                             1      1-2    2    3   3   9                                          Example 2                                                                             1      1-2    2    3   5   9                                          Example 3                                                                             1      1-2    2    3   3   9                                          Example 4                                                                             1      1-2    2    2   2   3   3   7   9                              Example 5                                                                             1      1-2    2    2   3   3   3   8   9                              Example 6                                                                             1      1-2    2    2   2   3   3   5   9                              Example 7                                                                             1      2      3    3   9                                              Example 8                                                                             1-2    3-4    3    3   5   5   5   6   9                              Example 9                                                                             1-2    3      3    3   3   5   5   6   9                              Example 10                                                                            1-2    3-4    3    3   5   5   5   6   9                              Example 11                                                                            1      1-2    1-2  2   2   3   3   3   5    7                         Example 12                                                                            1      1-2    2    2   2   3   3   5   7    9                         Example 13                                                                            1      1-2    2    2   3   3   3   5   6    9                         Example 14                                                                            1      1-2    2    2   3   3   3   5   6    7                         Example 15                                                                            1      1-2    2    2   2   3   3   5   5    6                         Example 16                                                                            1      1-2    2    2   2   3   3   5   5    6                         Example 17                                                                            1      1      1-2  2   3   3   5   9                                  Example 18                                                                            1      2      3    3   5   5   7   9                                  Example 19                                                                            1      1      2    3   5   9                                          Example 20                                                                            1      1      2    2   3   3   3   9                                  Example 21                                                                            1      2      2    3   3   5   5   9                                  Example 22                                                                            1      1      2    2   3   9                                          Compara-                                                                              1-2    9                                                              tive                                                                          Example 1                                                                     Compara-                                                                              4-5    5      7    7   9                                              tive                                                                          Example 2                                                                     Compara-                                                                              1      2      8    9                                                  tive                                                                          Example 3                                                                     Compara-                                                                              1      2      8    9                                                  tive                                                                          Example 4                                                                     Compara-                                                                              1      2      8    9                                                  tive                                                                          Example 5                                                                     Compara-                                                                              1      2      8    9                                                  tive                                                                          Example 6                                                                     Compara-                                                                              1      2      8    9                                                  tive                                                                          Example 7                                                                     Compara-                                                                              1      2      8    9                                                  tive                                                                          Example 8                                                                     Compara-                                                                              1      7      9                                                       tive                                                                          Example 9                                                                     Compara-                                                                              1      2      5    9                                                  tive                                                                          Example 10                                                                    ______________________________________                                    

EXAMPLE 23

A composition consisting of 100 parts of polyvinyl chloride (degree ofpolymerization=800), 20 parts of dioctyl phthalate (plasticizer), 1 partof calcium stearate, 2 parts of zinc stearate, and 1 part of saidethylene- vinyl acetate copolymer hydrolysate (C-1; auxiliarystabilizer) was subjected to preliminary mixing and then, kneading usinga 6"(dia.)×12" roll at 170° C. for 5 minutes to provide a 0.5 mm thicksheet.

In the course of kneading, the development of plate-out phenomenon wasmonitored. From the resulting sheet, a 50×60 mm testpiece was cut outand allowed to stand in a gear oven at 170° C. for a thermal stabilitytest.

EXAMPLES 24 TO 28

Sheets were manufactured and tested in the same manner as in Example 23except that in liew of 1 part of ethylene-vinyl acetate copolymerhydrolysate (C-1), 1 part of (C-2) (Example 24), 1 part of (C-3a)(Example25), 1 part of (C-3b) (Example 26), 1 part of (C-3c) (Example27) or 0.5 part of (C-1) (Example 28) was used.

COMPARATIVE EXAMPLE 11

The procedure of Example 23 was repeated except that the auxiliarystabilizer was omitted from the formulation of Example 23.

COMPARATIVE EXAMPLE 12

The procedure of Example 23 was repeated except that 1 part ofethylene-vinyl acetate copolymer hydrolysate (C-3d) was used as theauxiliary stabilizer.

COMPARATIVE EXAMPLE 13 TO 15

The procedure of Example 23 was repeated except that 1 part of finelydivided pentaerythritol (Comparative Example 13), 1 part of triphenylphosphite (Comparative Example 14) or 1 part of epoxidized soybean oil(Comparative Example 15) was used as the auxiliary stabilizer.

COMPARATIVE EXAMPLE 16

The procedure of Example 23 was repeated except that calcium stearatewas used in a proportion of 0.05 part, the addition of zinc stearateomitted, and 1 part of ethylene-vinyl acetate copolymer hydrolysate(C-3d) used as the auxiliary stabilizer.

COMPARATIVE EXAMPLE 17

The procedure of Example 23 was repeated except that 1 part of polyvinylalcohol with a degree of polymerization of 600 and a saponificationdegreeof 99 mole % was used as the auxiliary stabilizer.

EXAMPLES 29 AND 30

The procedure of example 23 was repeated except that 1 part ofethylene-vinyl acetate copolymer hydrolysate (C-5) (Example 29) or 1part of ethylene-vinyl acetate copolymer hydrolysate (C-6) (Example 30)was used as the auxiliary stabilizer.

The results obtained in Examples 23 to 30 and Comparative Examples 11 to17are shown in Table 2.

The evaluation of plate-out was made according to the following 4-graderating schedule.

⊚ No plate-out

∘ Substantially no plate-out

Δ Slight plate-out

x Marked plate-out

The initial coloration was evaluated at 15 minutes after commencement ofheating.

                  TABLE 2                                                         ______________________________________                                                Thermal stability                                                             Blacken-                                                                              Complete                                                              ing     Blacken- Initial                                                      begins  ing      discolor-                                                    (min.)  (min.)   ation      Plate-out                                 ______________________________________                                        Example 23                                                                              60        70       Nil      ⊚                        Example 24                                                                              60        70       Nil      ⊚                        Example 25                                                                              55        65       Pale orange                                                                            ⊚ -∘         Example 26                                                                              50        60       Light orange                                                                           ∘                           Example 27                                                                              50        60       Light orange                                                                           ∘                           Example 28                                                                              30        40       Nil      ⊚                        Example 29                                                                              60        65       Nil      ⊚ -∘         Example 30                                                                              55        60       Pale orange                                                                            ⊚ -∘         Comparative                                                                             <10       15       Nil      ⊚                        Example 11                                                                    Comparative                                                                             50        60       Orange   Δ                                 Example 12                                                                    Comparative                                                                             >80       >80      Nil      x                                       Example 13                                                                    Comparative                                                                             30        50       Nil      Δ                                 Example 14                                                                    Comparative                                                                             Sudden    30       Light orange                                                                           Δ                                 Example 15                                                                              black-                                                                        ening                                                                         after                                                                         30 min.                                                             Comparative                                                                             (brown-   (Brown-  Brown    Δ                                 Example 16                                                                              ing)      ing)                                                                <10       15                                                        Comparative                                                                             <10       15       Orange   Δ                                 Example 17                                                                    ______________________________________                                    

EXAMPLE 31

A composition consisting of 100 parts of vinylidene chloride-methylacrylate copolymer (methyl acrylate content 7 mole %), 10 parts ofdioctylphthalate, 1 part of calcium stearate, 2 parts of zinc stearateand 1 part of ethylene-vinyl acetate copolymer hydrolysate (C-1) wasextrusion-moldedand the resulting 0.5 mm thick sheet was allowed tostand in a gear oven at170° C. for testing its thermal stability.

The extrusion conditions were as follows.

Extruder: 40 mm (dia.)

Screw: L/D 23, compression ratio 3.2

Cylinder temperature (MAX): 170° C.

Head temperature: 170° C.

Die temperature: 170° C.

The thermal stability test showed a complete blackening time of 30minutes.

Where the addition of (C-1) was omitted, the control sample underwentcomplete blackening in 10 minutes.

EXAMPLE 32

A composition consisting of 100 parts of chlorinated polyethylene (Clcontent 40%), 30 parts of dioctyl phthalate, 1 part of triazine typevulcanizing agent, 2 parts of mercaptobenzothiazole type vulcanizationaccelerator, 1 part of calcium stearate, 2 parts of zinc stearate and 1part of ethylene-vinyl acetate copolymer hydrolysate (C-1) was molded(kneading by roll at 140° C. for 5 min.; vulcanizing at 160°C. for 20min.) to give a 1 mm thick sheet.

This sheet was subjected to a thermal stability test in a gear oven at180° C. The complete blackening time was 30 minutes.

On the other hand, the control sample free of (C-1) showed a completeblackening time of 10 minutes.

What is claimed is:
 1. A halogen-containing thermoplastic resincomposition comprising a halogen-containing thermoplastic resin (A), ametallic soap (B) and an ash- and alkali metal-lean ethylene-vinylacetate copolymer hydrolysate (C) having an ethylene content of 20 to 75mole percent, a degree of saponification not less than 50 mole percent,an ash content not exceeding 300 ppm and an alkali metal content notexceeding 200 ppm, the proportions of (B) and (C) based on 100 parts byweight of (A) being 0.1 to 5 parts by weight and 0.1 to 5 parts byweight, respectively.
 2. The composition of claim 1 wherein saidhalogen-containing thermoplastic resin (A) is a polyvinyl chlorideresin.
 3. The composition of claim 1 wherein at least a portion of saidmetallic soap (B) is a zinc metallic soap.
 4. The composition of claim 1wherein said ethylene-vinyl acetate copolymer hydrolysate (C) has an ashcontent not exceeding 50 ppm and an alkali metal content not exceeding35 ppm.
 5. The composition of claim 1 wherein said ethylene-vinylacetate copolymer hydrolysate (C) has an ash content not exceeding 20ppm and an alkali metal content not exceeding 5 ppm.
 6. The compositionof claim 1 wherein the weight ratio of said ethylene-vinyl acetatecopolymer hydrolysate (C) to said metallic soap (B) is in the range of0.05 to 2.